Testicular androgen is vital in the initiation and maintenance of spermatogenesis and sperm maturation. We propose to describe the androgen transport systems within the testis and epididymis and to define their functions in androgen action on the germinal epithelium and epididymis. Objectives: a. Identify and characterize the carrier protein (androgen binding protein, ABP) and receptor proteins in testis and epididymis (monkey and human). b. Differentiate the gonadotrophin regulation (LH vs. FSH) of testicular androgen carrier and receptor systems. c. Measure influence of carrier protein on androgen concentrations in seminiferous tubules and epididymal segments. d. Identify the cell types containing androgen receptors (sites of androgen action) in germinal epithelium and epididymis. e. Identify organ specific properties of the intracellular transport systems in testis and epididymis. f. Define the functional roles of carrier and intracellular receptor systems in androgen action on cell proliferation and metabolism in testis and epididymis. g. Delineate maturational changes in the carrier-receptor systems in relation to the maturation of steroidogenesis, spermatogenesis, and epididymal function. Methods: Physicochemical methods of protein separation, quantitative binding assay for carrier protein, bioassay and radioimmunoassay of gonadotrophins, competitive protein binding assays for androgen, isolation of germ cells, autoradiography and histology (germinal epithelium and epididymis), steroid biochemistry, enzyme assays, molecular biology of RNA, DNA.